DuPont and Chemours have agreed to pay $670 million to settle 3,550 lawsuits in Ohio and West Virginia by residents who say they were sickened by drinking water contaminated by perfluorooctanoic acid (PFOA) released from a former DuPont plant in Parkersburg, W.Va.

The deal could make it easier for plaintiffs in other regions to pursue similar cases involving PFOA, a processing aid used until 2015 . . .